Project 2: A central concept of motor control is that actions are represented by motor programs. The overarching goal of this research is to characterize the neural substrates of motor program formation in humans. This will be pursued with brain mapping studies that characterize four essential components of successful motor programming, error correction, integration and automatization. Specific Aim 1. Identify the neural substrates involved in on-line error correction. Rapid movements are programmed in advance, although they can be adjusted or reprogrammed on-line in the face of inaccuracy or a changing movement goal. It is hypothesized that motor programs are modified (either amended or reprogrammed) with both forward models of an action as well as delayed feedback from the periphery. The role of parietal and premotor cortex for reprogramming a movement will be tested with functional MRI and transcranial magnetic stimulation. Specific Aim 2: Determine the functional areas used to adapt a motor program to changing task demands. Adaptation is the process of adjusting a previously learned action in the face of changing musculoskeletal or environmental constraints. It is hypothesized that the cerebellum will be essential for adapting a movement to a new behavior context. Specific Aim 3. Characterize the functional systems used to integrate motor programs. The underlying hypothesis is that complex movements are learned in part through the integration of submovements. It is hypothesized that basal ganglia-thalamo-cortical loops projecting to SMA and motor cortex are essential for linking of movements into larger motor sets. Specific Aim 4. Investigate the changes that occur in neural systems as motor programs are automatized. It is hypothesized that extensive practice and the emergence of skill automatization are accompanied by a shift of activity from motor association cortex to parietal systems involved in more abstract representations of movement. The behavioral tasks in this project are complementary to experiments proposed in non-human primates by other investigators of this program project. The results will provide fundamental insight into neural systems involved in motor program control and plasticity.